The overall aim is to determine what role PDGF plays in mammalian development. There is evidence that the PDGF-A gene is expressed in preimplantation mouse embryos while the B chain appears later in development, and in accord, the receptor that responds to the A chain (alpha receptor) appears before the beta receptor. Therefore, this study will focus on the early roles of the A chain and the alpha receptor on the development of the pre- and peri-implantation embryo. The specific aims are as follows: 1. to select those transgenic animals from those that have already been prepared that express excess amounts of PDGF or that have lower levels than the normal animal, and determine the effects of further inducing the transgene with zinc. Selected females will be induced with zinc in the drinking water during gestation to determine the correlations with developmental abnormalities. 2. To prepare antibodies to PDGFs and alpha and beta receptors for detection and quantitation of these polypeptides in transgenic mouse tissues. In addition, by making antibodies to the sites that are involved in ligand binding, we hope to select antisera that will block ligand binding to test the effect on embryo development in vitro. 3. To make a dominant negative construct for PDGF-R-alpha. A carboxyterminal truncated construct will be introduced in an expression vector to interfere with normal alpha receptor function and hence, determine the biological and developmental consequences of inactivated PDGF-receptors in vitro and in vivo. These studies will determine the roles of PDGF growth factors and their receptors in the processes of early cell division and cell differentiation. These animals will also be useful in studying the later consequences of abnormal PDGF and receptor levels in vascular disease and in tumor progression.